@babel/plugin-proposal-class-properties does not work with CRA 2.0

Install react-scripts@2.0.0-next.3e165448 and use a package with classProperties, for example @material/react-top-app-bar, you will get this error:

...
 Support for the experimental syntax 'classProperties' isn't currently enabled
...
Add @babel/plugin-proposal-class-properties (https://git.io/vb4SL) to the 'plugins' section of your Babel config to enable transformation.

[gaearon]

folks at Google feel like the experimental ES features are here to stay

I think this might be a misunderstanding of some sort. I was physically present at a TC39 meeting just a few months ago, and I can assure you the current behavior or syntax of class properties was not by any means considered final.

I understand that CRA is trying to be highly opinionated, but some of these opinions seems to fall out of the scope of React itself. In my opinion, CRA should be be opinionated in the relevant scope, and not try to babysit its users when it comes to making decisions outside of that scope.

Respectfully, I understand your position, but the vast majority of the users of this library won’t know what they’re getting into (just like you didn’t). If the spec changes in half a year, and all of the code published using it will stop compiling in the next version of CRA that updates Babel, people will blame React and the React ecosystem for the churn.

And in a way, they’ll be right. Compiling third-party code with transforms specified by the app tooling is very fragile, as proven by years of watching frustrated React Native users (who adopted this approach and regretted it quite a few times). And beginners (who might not know how to run a codemod, or what to do when we break their code) will be hurt the most. Given that CRA’s goal is to make React easy to get started with, this seems like it a direct contradiction to its mission.

Being the only official project in the React ecosystem related to build tooling, I see it as our responsibility to try to ensure our users don’t shoot themselves in the foot, even if at the time they think it’s best for them.

[bidanjun]

as a example,for react-navigation,it’s published as source code in npm. it use react-navigation-deprecated-tab-navigator, also it’s publish using source code without compile,so ./node_modules/react-navigation-deprecated-tab-navigator/src/views/TabBarBottom.js SyntaxError: D:.…\node_modules\react-navigation-deprecated-tab-navigator\src\views\TabBarBottom.js: Support for the experimental syntax ‘classProperties’ isn’t currently enabled (26:23):

and is there any way to use it without eject?